THESIS APPROVAL
THESIS APPROVAL
THESIS APPROVAL
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Lumbriculus variegatus ceased at least two days before fragmentation.<br />
The size group of L. hoffmeisteri established from the experiment was<br />
separated into four categories based on length measurement, consisted of big and long<br />
adult worms (3.0-3.5 cm), two sizes of immature worms (2.0-2.5 and 1.0-1.5 cm) and<br />
small newly hatched worms (0.3-0.5 cm). The index of size observation in this study<br />
is in contrast to previous study concerning the determination of this worm species by<br />
using the width of the ninth segment which contains the penis tube (Raburu et al.,<br />
2002). However, by the same author, length measurement was used to group another<br />
freshwater oligochaete, Branchiura sowerbyi. The method of classification using<br />
length-frequency was adopted since there was no sign of sexual maturity and evidence<br />
of any cocoon appearing in individuals. Furthermore, truly distinction of immature,<br />
breeding and mature worms was so difficult in this study. Ladle (1971) found that<br />
immature and breeding worms are not easy to distinguish either by chaetal<br />
characteristics and the presence of spermatophores. Classification of L. hoffmeisteri<br />
is further complicated by the fact that sexually mature worms resorb the penis tube<br />
after reproduction (Kennedy, 1966; Ladle, 1971; Aston, 1973; Poddubnaya, 1980) and<br />
revert to an immature condition which cannot be differentiate from a juvenile worm.<br />
From this reason, the size group of L. hoffmeisteri from this study was then<br />
established only by grouping the worms into four categories as stated in the results.<br />
3.2 Biological Activities<br />
In E-WH, the accumulation of TOM of the sediment had been observed<br />
around 28 d, followed by the decline of organic matter occurring between d 35 and<br />
d 42 of the experiment with an increasing of L. hoffmeisteri colonies. These results<br />
indicated that such an increase in number of individual and weight of worms had<br />
enhanced the decrease of TOM in the sediment. The number of individual and weight<br />
of the worms increased due to individual growth and reproduction. In addition, these<br />
worms provide an affect to sediment geochemical processes via bioturbation (Rice<br />
and Rhoads, 1989). Bioturbation is the process of sediment mixing by benthic<br />
animals (Gage and Tyler, 1991). Oligochaetes are assumed to have a significant<br />
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